Snow Stratigraphy and Accumulation (SPQMLT UI)
1964 3 is essentially a large wooden shelter on iron runners that houses a drilling rig and sleeping quarters.
Snow Stratigraphy and Accumulation (SPQMLT UI)
On three occasions, the expedition was resupplied with fuel and parts needed to repair equipment. The supplies were air-dropped to the party by Navy LC— 130 aircraft from McMurdo Station. 2 A special radar beacon, loaned by the Navy, helped guide the aircraft to the party's location. Cairns, built of empty fuel drums, were erected at the sites of the airdrops.
ARTHUR S. RUNDLE
No unusual topographic features were discovered. The terrain was generally flat, and its surface layer consisted of hard-packed snow. The weather was favorable, the temperature ranging from —40°C. to —10°C. and the wind rarely exceeding 10 knots. Severe whiteouts occurred during the final week of travel. Vehicle breakdowns cost considerable travel time, but outstanding work by the two engineers kept the loss as low as possible. On January 30 and 31, SPQMLT III ended when the personnel, equipment, snow samples, and one Sno-Cat were airlifted to McMurdo Station on two flights by Navy LC-130 aircraft.
Scientific Procedures Weather observations were made every six hours during the period of the traverse. A profile of the ice cap's thickness was obtained en route by means of a continuously recording radio-sounding device. Every 8 km (5 miles), the traverse halted for a few minutes to permit measurements of local gravity, surface elevation, snow density, and snow-accumulation rate. Every 65 km (40 miles), a major station was established at which the following investigations were made: (1) The geographic position of the station and a true bearing were determined by celestial observations; (2) the intensity and direction of the magnetic field were measured; (3) a 50-m hole was drilled and the temperature and density of the ice at selected depths were measured; (4) the thickness of the ice cap was measured by the seismic-reflection method; (5) a 3-rn-deep pit was dug to obtain snow samples for later chemical studies; and (6) the near-surface stratigraphy, density, and accumulation rate of snow were studied and measured. At one of the major stations, a difficult seismic-refraction experiment was accomplished. The scientific programs conducted on the traverse are discussed more fully in the following articles. "Antarctic Journal, vol. III, no. 3, p. 72.
July-August 1968
Institute of Polar Studies Ohio State University In order to establish a snow-stratification and accumulation 'reference for investigations to be conducted along the route of SPQMLT III, investigations of these factors were conducted during late November and early December at Plateau Station. Snow accumulation was determined by the remeasurernent of the accumulation-stake network established there in February 1966. The remeasurement of the stake network showed an average accumulation between January 21 and November 25, 1967, of 5.7 cm (Gjessing, personal communication). These stakes, when again inspected by E. E. Picciotto on January 17, 1968, showed an additional average increment of 0.3 cm (Picciotto, personal communication). At 10 snow pits, the stratigraphy revealed an extensive, hard, fine-grained (wind-packed) surface layer. This layer, which is interpreted as having been formed by high winds during mid-November 1967 (Dingle, personal communication), contrasts with the hard, summer "sintered" layer described by Koerner (1968). The den sity of this upper layer, which accounted for more accumulation than that precipitated during the year 1967, was determined as 0.364 g/cm, indicating an accumulation of 2.07 g/crn 2 for that year. Direct interpretation of the pit stratigraphy, however, revealed an accumulation of 3.39 g/crn 2, suggesting that a more extensive sampling program would have been desirable. Along the traverse route, 168 shallow pits were excavated, one approximately every 8 km (5 miles), and examined for stratigraphic features and firn density. The criteria used in determining the annual horizons varied along the traverse route. They consisted of hard layers, crusts, depth hoar, and texture changes (particularly in grain size and shape). Numerous problems arose in the interpretation of the stratigraphy, the most notable being the frequent possibility of one year's layer being very thin or missing entirely as a result of erosion of the small annual increment. Thick layers, on the other hand, might be accounted for by redeposition. Frequently, the origins of the hard layers, hoar layers, and crusts were impossible to determine, and in many cases contradictory interpretations of the number of years represented in one section could be made. Periodically, however, an "indisputable" section was excavated, al95
14 4000 2 3600- -PfAL ii 3600 -
AVERAGE ANNUAL ACCUMULATION QUEEN MAUD LAND TRAVERSE 1967-1968 -
J \ 1A
-
A
I 9 3000
9 3000 26006 - 6 2400 5 2200
' ' J
-
N
7 2600 362400 5+
I
__
I 1400 0 I200RR__R
14 4(M 3 I2Tco
SEAD 550 SEX) 150 1875 2375 300 350 TRAVERSE MILES
700 750 RIX) 850
7rkOS 700S O'S 7 0S 72 OLOS 77395S WOS 70022O 7556O I75 389 i5S OS lOS 73OS 36OS 78*I95S II53E O932E OP13E O54 E O4l6E 01M6E 0005E OI55W 04OW O652W 4O3OE 36M3E 33I4E 29-43'E27O5E 23E 2OO5E I7IOE I425E PLATEAU STATION
g
Average annual accumulation, SPQMLT III
Mile
5 2.99 217.5 4.13 430 7.46640 14.36 10 3.00 222.5 4.23 435 6.72 645 9.81 15 2.00 227.5 5.07 440 7.73 650 9.75 20 2.83 232.5 4.88 445 6.51 655 11.79 25 2.88 237.5 5.76 450 6.78 660 9.88 30 2.62 242.5 5.07 455 5.98 665 8.48 35 2.83 247.5 5.19 460 5.90 670 9.03 40 1.89 252.5 5.96 465 6.66 675 9.11 45 1.78 257.5 5.08 470 5.87 680 9.39 50 2.95 262.5 5.92 475 6.74 685 9.23 55 2.65 267.5 6.28 480 6.32 690 9.89 60 2.93 272.5 5.72 485 8.22 695 9.80 65 3.29 277.5 6.33 490 6.99 700 9.87 70 3.61 282.5 5.26 495 6.09 705 10.46 75 2.01 287.5 4.42 500 7.50 710 8.80 80 1.83 292.5 4.37 505 8.85 715 8.81 85 2.88 300 5.73 510 6.64 720 8.31 90 2.63 305 5.11 515 7.89 725 7.47 95 3.24 310 4.63 520 8.85 730 8.17 100 3.07 351 6.19 525 8.05 735 7.66 105 2.96 320 5.67 530 6.50 740 7.98 110 3.58 325 6.30 535 7.02 745 9.15 115 3.27 330 6.33 540 6.45 750 8.57 120 3.58 335 5.70 545 6.58 755 9.49 125 3.24 340 5.98 550 9.07 760 9.07 130 3.28 345 5.41 555 9.01 765 8.97 135 3.01 350 5.99 560 7.29 770 9.65 140 3.29 355 5.53 565 6.59 775 9.09 145 3.34 360 4.70 570 7.12 780 9.35 150 3.58 365 6.05 575 7.19 785 8.80 155 3.95 370 6.20 580 9.28 790 9.35 160 3.73 375 4.44 585 8.26 795 9.87 165 3.32 380 5.17 590 10.38 800 9.91 170 3.90 385 5.28 595 8.05 805 9.95 175 4.41 390 5.58 600 11.68 810 10.00 180 4.05 395 6.13 605 9.38 815 9.93 187.5 4.38 400 6.35 610 9.89 820 9.13 192.5 4.94 405 6.28 615 10.25 825 9.12 197.5 4.48 410 6.99 620 9.92 830 9.87 202.5 5.55 415 7.26 625 10.03 835 11.32 207.5 4.85 420 6.62 630 10.44 840 10.38 212.5 4.36 425 6.48 635 10.32
1. Modest reliability can be claimed for stratigraphic interpretations in this area of low annual accumulation, although the interpretations are by no means as reliable as those made at South Pole and Byrd Stations, where the accumulation is higher and the stratigraphy less complex. 2. Because of the complex stratigraphy, it is highly desirable to study several shallow pits at one site or to space the excavations more closely over the traverse route. The interpretation of deeper pits at widely spaced locations might not be possible without the shallow-pit investigations. Acknowledgments. The author is grateful to Mr. Carl K. Poster, Geophysical and Polar Research Center, University of Wisconsin, for information on surface elevations along the traverse route. This program was supported under National Science Foundation grant GA-1076 to the Ohio State University Research Foundation. Reference Koerner, R. M. 1968. The Stratigraphic Method of Deter-
mining the Snow Accumulation Rate at Plateau Station, Antarctica: A New Approach. Unpublished manuscript.
Institute of Polar Studies, Ohio State University.
1
Ice-Thickness Investigations on lowing, by projection, an acceptable interpretation of the more confused sections. In this way, a value for the average accumulation over the past 2-5 years was calculated for each station (see table and figure). These results conform with the expectation that accumulation increases with decreasing elevation and distance from the coast. The apparent levelling-off of the values toward the end of the traverse route, in spite of a continued loss of elevation, might be explained by the compensating factor of increasing distance from the coast. The following overall conclusions have been drawn from the foregoing aspect of the glaciological program: 96
SPQMLT III J . W. CLOUGH, C. R. BENTLEY, and C. K. POSTER Department of Geology and Geophysics University of Wisconsin (Madison) Elevations of the ice surface along the traverse route were measured with 11 temperature-corrected aneroid altimeters. Simultaneous altimeter readings were made at 8-km (5-mile) intervals, and nearly continuous readings were made with a single altimeter. ANTARCTIC JOURNAL
Snow Stratigraphy and Accumulation (SPQMLT UI)
On three occasions, the expedition was resupplied with fuel and parts needed to repair equipment. The supplies were air-dropped to the party by Navy LC— 130 aircraft from McMurdo Station. 2 A special radar beacon, loaned by the Navy, helped guide the aircraft to the party's location. Cairns, built of empty fuel drums, were erected at the sites of the airdrops.
ARTHUR S. RUNDLE
No unusual topographic features were discovered. The terrain was generally flat, and its surface layer consisted of hard-packed snow. The weather was favorable, the temperature ranging from —40°C. to —10°C. and the wind rarely exceeding 10 knots. Severe whiteouts occurred during the final week of travel. Vehicle breakdowns cost considerable travel time, but outstanding work by the two engineers kept the loss as low as possible. On January 30 and 31, SPQMLT III ended when the personnel, equipment, snow samples, and one Sno-Cat were airlifted to McMurdo Station on two flights by Navy LC-130 aircraft.
Scientific Procedures Weather observations were made every six hours during the period of the traverse. A profile of the ice cap's thickness was obtained en route by means of a continuously recording radio-sounding device. Every 8 km (5 miles), the traverse halted for a few minutes to permit measurements of local gravity, surface elevation, snow density, and snow-accumulation rate. Every 65 km (40 miles), a major station was established at which the following investigations were made: (1) The geographic position of the station and a true bearing were determined by celestial observations; (2) the intensity and direction of the magnetic field were measured; (3) a 50-m hole was drilled and the temperature and density of the ice at selected depths were measured; (4) the thickness of the ice cap was measured by the seismic-reflection method; (5) a 3-rn-deep pit was dug to obtain snow samples for later chemical studies; and (6) the near-surface stratigraphy, density, and accumulation rate of snow were studied and measured. At one of the major stations, a difficult seismic-refraction experiment was accomplished. The scientific programs conducted on the traverse are discussed more fully in the following articles. "Antarctic Journal, vol. III, no. 3, p. 72.
July-August 1968
Institute of Polar Studies Ohio State University In order to establish a snow-stratification and accumulation 'reference for investigations to be conducted along the route of SPQMLT III, investigations of these factors were conducted during late November and early December at Plateau Station. Snow accumulation was determined by the remeasurernent of the accumulation-stake network established there in February 1966. The remeasurement of the stake network showed an average accumulation between January 21 and November 25, 1967, of 5.7 cm (Gjessing, personal communication). These stakes, when again inspected by E. E. Picciotto on January 17, 1968, showed an additional average increment of 0.3 cm (Picciotto, personal communication). At 10 snow pits, the stratigraphy revealed an extensive, hard, fine-grained (wind-packed) surface layer. This layer, which is interpreted as having been formed by high winds during mid-November 1967 (Dingle, personal communication), contrasts with the hard, summer "sintered" layer described by Koerner (1968). The den sity of this upper layer, which accounted for more accumulation than that precipitated during the year 1967, was determined as 0.364 g/cm, indicating an accumulation of 2.07 g/crn 2 for that year. Direct interpretation of the pit stratigraphy, however, revealed an accumulation of 3.39 g/crn 2, suggesting that a more extensive sampling program would have been desirable. Along the traverse route, 168 shallow pits were excavated, one approximately every 8 km (5 miles), and examined for stratigraphic features and firn density. The criteria used in determining the annual horizons varied along the traverse route. They consisted of hard layers, crusts, depth hoar, and texture changes (particularly in grain size and shape). Numerous problems arose in the interpretation of the stratigraphy, the most notable being the frequent possibility of one year's layer being very thin or missing entirely as a result of erosion of the small annual increment. Thick layers, on the other hand, might be accounted for by redeposition. Frequently, the origins of the hard layers, hoar layers, and crusts were impossible to determine, and in many cases contradictory interpretations of the number of years represented in one section could be made. Periodically, however, an "indisputable" section was excavated, al95
14 4000 2 3600- -PfAL ii 3600 -
AVERAGE ANNUAL ACCUMULATION QUEEN MAUD LAND TRAVERSE 1967-1968 -
J \ 1A
-
A
I 9 3000
9 3000 26006 - 6 2400 5 2200
' ' J
-
N
7 2600 362400 5+
I
__
I 1400 0 I200RR__R
14 4(M 3 I2Tco
SEAD 550 SEX) 150 1875 2375 300 350 TRAVERSE MILES
700 750 RIX) 850
7rkOS 700S O'S 7 0S 72 OLOS 77395S WOS 70022O 7556O I75 389 i5S OS lOS 73OS 36OS 78*I95S II53E O932E OP13E O54 E O4l6E 01M6E 0005E OI55W 04OW O652W 4O3OE 36M3E 33I4E 29-43'E27O5E 23E 2OO5E I7IOE I425E PLATEAU STATION
g
Average annual accumulation, SPQMLT III
Mile
5 2.99 217.5 4.13 430 7.46640 14.36 10 3.00 222.5 4.23 435 6.72 645 9.81 15 2.00 227.5 5.07 440 7.73 650 9.75 20 2.83 232.5 4.88 445 6.51 655 11.79 25 2.88 237.5 5.76 450 6.78 660 9.88 30 2.62 242.5 5.07 455 5.98 665 8.48 35 2.83 247.5 5.19 460 5.90 670 9.03 40 1.89 252.5 5.96 465 6.66 675 9.11 45 1.78 257.5 5.08 470 5.87 680 9.39 50 2.95 262.5 5.92 475 6.74 685 9.23 55 2.65 267.5 6.28 480 6.32 690 9.89 60 2.93 272.5 5.72 485 8.22 695 9.80 65 3.29 277.5 6.33 490 6.99 700 9.87 70 3.61 282.5 5.26 495 6.09 705 10.46 75 2.01 287.5 4.42 500 7.50 710 8.80 80 1.83 292.5 4.37 505 8.85 715 8.81 85 2.88 300 5.73 510 6.64 720 8.31 90 2.63 305 5.11 515 7.89 725 7.47 95 3.24 310 4.63 520 8.85 730 8.17 100 3.07 351 6.19 525 8.05 735 7.66 105 2.96 320 5.67 530 6.50 740 7.98 110 3.58 325 6.30 535 7.02 745 9.15 115 3.27 330 6.33 540 6.45 750 8.57 120 3.58 335 5.70 545 6.58 755 9.49 125 3.24 340 5.98 550 9.07 760 9.07 130 3.28 345 5.41 555 9.01 765 8.97 135 3.01 350 5.99 560 7.29 770 9.65 140 3.29 355 5.53 565 6.59 775 9.09 145 3.34 360 4.70 570 7.12 780 9.35 150 3.58 365 6.05 575 7.19 785 8.80 155 3.95 370 6.20 580 9.28 790 9.35 160 3.73 375 4.44 585 8.26 795 9.87 165 3.32 380 5.17 590 10.38 800 9.91 170 3.90 385 5.28 595 8.05 805 9.95 175 4.41 390 5.58 600 11.68 810 10.00 180 4.05 395 6.13 605 9.38 815 9.93 187.5 4.38 400 6.35 610 9.89 820 9.13 192.5 4.94 405 6.28 615 10.25 825 9.12 197.5 4.48 410 6.99 620 9.92 830 9.87 202.5 5.55 415 7.26 625 10.03 835 11.32 207.5 4.85 420 6.62 630 10.44 840 10.38 212.5 4.36 425 6.48 635 10.32
1. Modest reliability can be claimed for stratigraphic interpretations in this area of low annual accumulation, although the interpretations are by no means as reliable as those made at South Pole and Byrd Stations, where the accumulation is higher and the stratigraphy less complex. 2. Because of the complex stratigraphy, it is highly desirable to study several shallow pits at one site or to space the excavations more closely over the traverse route. The interpretation of deeper pits at widely spaced locations might not be possible without the shallow-pit investigations. Acknowledgments. The author is grateful to Mr. Carl K. Poster, Geophysical and Polar Research Center, University of Wisconsin, for information on surface elevations along the traverse route. This program was supported under National Science Foundation grant GA-1076 to the Ohio State University Research Foundation. Reference Koerner, R. M. 1968. The Stratigraphic Method of Deter-
mining the Snow Accumulation Rate at Plateau Station, Antarctica: A New Approach. Unpublished manuscript.
Institute of Polar Studies, Ohio State University.
1
Ice-Thickness Investigations on lowing, by projection, an acceptable interpretation of the more confused sections. In this way, a value for the average accumulation over the past 2-5 years was calculated for each station (see table and figure). These results conform with the expectation that accumulation increases with decreasing elevation and distance from the coast. The apparent levelling-off of the values toward the end of the traverse route, in spite of a continued loss of elevation, might be explained by the compensating factor of increasing distance from the coast. The following overall conclusions have been drawn from the foregoing aspect of the glaciological program: 96
SPQMLT III J . W. CLOUGH, C. R. BENTLEY, and C. K. POSTER Department of Geology and Geophysics University of Wisconsin (Madison) Elevations of the ice surface along the traverse route were measured with 11 temperature-corrected aneroid altimeters. Simultaneous altimeter readings were made at 8-km (5-mile) intervals, and nearly continuous readings were made with a single altimeter. ANTARCTIC JOURNAL
